Results :Before shunt was put in water content in the subependymal tissue immediate underneath the ependymal cells was 72.2+__-l. 0 % and much increased than the water content of deep white matter tissue of 67.2 +__- 0.7 % The results indicate that water content is definitely increased just underneath the ventricular surface but increased than the water content of deep white matter tissue of 67.2+__-0.7 %. In the animals in which shunt did work, its water content in the subependymal tissue was 70.9+__-1.1% and this was not different from the control animals. In animals which failed to function after shunting water content did not decreased as might be expected and interestingly enough its water content in the deeper tissue was increased. Electron microscopic examination, however, did not show marked enlargement of the extracellular space in the deep white matter and also derangement of the axons and myelin fibers were not prominent at all.From the series of our experiment it was learned that if shunt procedure failed to reduce the ventricular size water content in the deep white matter, when say that it is only 2 or 3 mm from the ependymal surface though increased definitely suggesting an important role of the subependymal tissue as a subsidiary way of cerebrospinal fluid circulation.